Memebrane proteins and Transport mechanisms

What is a membrane protein?

A protein molecule attached to or associated with the cell membrane.

How many main types of membrane proteins are there?

Two: integral and peripheral.

What is an integral membrane protein?

A protein embedded through the phospholipid bilayer.

What is a peripheral membrane protein?

A protein loosely attached to the surface of the membrane.

Define solute.

The substance that dissolves in a solvent.

Define solvent.

The substance capable of dissolving solutes to form a solution.

What is the most common solvent in biology?

Water.

Define solution.

A mixture of solute and solvent.

Define osmosis.

The diffusion of water across a membrane without energy input.

In which direction does water move during osmosis?

From low solute concentration to high solute concentration.

Why does osmosis not require energy?

Water and solute molecules move randomly and naturally.

Why must osmosis be described using solute concentration?

Because both solute and solvent are involved.

What is water potential?

A measure related to solute concentration affecting water movement.

What is the correct way to describe osmosis using water potential?

Water moves from higher water potential to lower water potential.

What are aquaporins?

Specialised integral proteins that allow water to pass through membranes.

Why are aquaporins needed?

Water has difficulty passing through the hydrophobic center of the bilayer.

Define facilitated diffusion.

Passive movement of molecules across membranes using transport proteins.

Which molecules use facilitated diffusion?

Large, polar molecules and ions.

What two types of proteins mediate facilitated diffusion?

Channel proteins and carrier proteins.

What is a channel protein?

A protein that allows specific ions or molecules to pass along a concentration gradient.

What is a carrier protein?

A protein that binds a solute and changes shape to move it across the membrane.

Why are channel proteins selective?

They are selective based on size, charge, voltage, or binding.

Give an example of a selective channel protein.

Potassium channels in nerve cells.

What type of channel are potassium channels?

Voltage-gated channels.

Define active transport.

Movement of molecules against a concentration gradient using energy.

What energy source is used in active transport?

ATP.

Give one example of a protein pump.

The sodium-potassium pump in nerve cells.